Ring size guide: get it close, keep the surprise
Updated November 2026
You don't need the exact size — you need to be within one size, buying a ring that can be adjusted, from a seller who'll resize it free or cheap. Here's how to get there without a suspicious "hey, what's your ring size?" text.
Quick answer: the average women's ring size is 6 to 6.5; men's is 9 to 10. When guessing, err one half-size large — sizing a ring down is easier and cheaper than stretching it up. Most resizes cost $50–$150.
US sizes to millimeters
| US size | Diameter | US size | Diameter |
|---|---|---|---|
| 4 | 14.9 mm | 7 | 17.3 mm |
| 5 | 15.7 mm | 8 | 18.1 mm |
| 5.5 | 16.1 mm | 9 | 19.0 mm |
| 6 | 16.5 mm | 10 | 19.8 mm |
| 6.5 | 16.9 mm | 11 | 20.6 mm |
Finding the size without blowing the surprise
- Borrow a ring she already wears — ideally on the left ring finger or right ring finger (close enough). Trace the inside circle on paper, or press it gently into a bar of soap, and measure the diameter against the chart above. Return it before it's missed.
- Photograph a ring next to a coin for scale if borrowing is too risky, and let a jeweler work out the size.
- Recruit an ally. A sister or best friend can get the number in one casual try-on at a mall kiosk.
- The "family ring" cover story. Mention a (fictional) relative's ring you might inherit and ask her size out of curiosity — risky but effective.
- When all else fails, buy a 6.5. It's the most common size and the easiest starting point to adjust from.
What resizing costs
| Job | Typical cost | Notes |
|---|---|---|
| Size down (up to 2 sizes) | $50–$100 | Metal is removed; the easier direction |
| Size up (up to 2 sizes) | $75–$150 | Metal is added; costs more in platinum and 18k |
| Pavé or detailed bands | $150–$350 | Stones near the resize point must be reset |
| Full eternity, tension, some channel-set rings | Often impossible | Stones or structure run the whole band — exchange instead of resize |
Before you buy: confirm the seller's resize policy in writing. The good online retailers and many independents include one free resize in the first year — that policy is worth real money when you're guessing at sizes. More in where to buy.